The American is best remembered for playing in the longest match at Wimbledon, his 11-hour epic against Nicolas Mahut eight years ago, and one of the biggest mysteries in men's tennis is how the big-serving Isner had never reached the second week on the London lawns.

The 33-year-old had to save match points against Belgian qualifier Ruben Bemelmans in the second round but he was a class above 98th-ranked Moldovan Radu Albot on Friday as he romped to 6-3 6-3 6-4 victory.

Isner's next opponent will be Greek teenager Stefanos Tsitsipas.

"Very satisfied right now to be in the second week and also have two days off. That's nice," Isner told reporters.

"I will certainly enjoy tomorrow. I don't get to work. Just sit on the couch all day. No pressure at all, sleep well tonight, will enjoy tomorrow.

"Get back to work really hard on Sunday."

Isner, the ninth seed, banged down 21 aces against Albot having served a whopping 64 against Bemelmans and says the hot, fast conditions are tailor-made for his game.

"I like my serve in any conditions, but these conditions are very, very good for it," the American said.

On his clash with Tsitsipas he said it will be a bit different to their last meeting in a freezing cold hall in Shanghai which he won in a couple of tiebreaks.

"That was a weird match. We moved indoors because of all the rain. Zero atmosphere. No one there. It was a bizarre match. Super-fast courts. I won two tiebreakers, but I can't draw anything from that," he said.

"He's certainly one of the best young players we have in the game today. He's got a lot of talent and a lot of ability, but maybe I have experience on my side. We'll see which one comes out on the better side of things on Monday."